This invention relates generally to radial structural components in gas turbine engines, and specifically to components with portions operating at temperatures exceeding 1200° F. In particular, the invention concerns replacing selected portions of a component with materials resistant to high temperature degradation.
Gas turbine engines are configured around a core comprising a compressor, a combustor and a turbine, which are arranged in flow series with a forward (upstream) inlet and an aft (downstream) exhaust. The compressor compresses air from the inlet, which is mixed with fuel in the combustor and ignited to produce hot combustion gas. The combustion gas drives the turbine, and is exhausted downstream. Typically, compressed air is also utilized to cool downstream engine components, particularly turbine parts exposed to hot working fluid flow.
The turbine section may be coupled to the compressor via a common shaft, or using a series of coaxially nested shaft spools, which rotate independently. Each spool includes one or more compressor and turbine stages, which are formed by alternating rows of blades and vanes. The working surfaces of the blades and vanes are formed into airfoils, which are configured to compress air from the inlet (in the compressor), or to extract energy from combustion gas (in the turbine).
In ground-based industrial gas turbines, power output is typically provided in the form of rotational energy, which is transferred to a shaft and used to drive a mechanical load such as a generator. Weight is not as great a factor in ground-based applications, and industrial gas turbines can utilize complex spooling systems for increased efficiency. Ground-based turbines are also commonly configured for combined-cycle operations, in which additional energy is extracted from the partially-cooled exhaust gas stream, for example by driving a steam turbine.
In gas turbine engine design, there is a constant need to balance the benefits of increased pressure and combustion temperature, which tend to improve engine performance, with accompanying wear and tear on the engine components, which tend to decrease service life. In particular, there is a need for materials that resist the increased thermal exposure in the compressor or turbine section of modern gas turbine engines.